Insulator for high-tension conductors.



A. AICHELE.

INSULATOR FOR HIGH TENSION cououcmns.

APPLICATION FILED NOV. 25. I913.

Patenwd May 15, 1917.

[nvenla'n rt Alb/Lei MM 1;:

UNITED STATES PATENT OFFICE.

ALBERT AICHELE, OFBADEN, swl 'rznanann, ASSIGNOR 'ro .AKTIENGESELLSCHAFTBROWN BOVERI5& c111, or BADEN, SWITZERLAND.

iics'rma'roa ronHIoH-rENsIoN commcroas.

To all wkomiganay concern:

Be it knowh'that I, ALBERT Aiouenn, a citizen of the Swiss Republic, andresiding at Wiesenstrasse 10, .Baden, Switzerland, have invented certainnew and useful Im- 'provements in and Relating to Insulators as thecoverof a transformer or an oil switch which is earthed. For convenience thishole in the metal wall is hereinafter referred to as a socket.

The object of the invention is to provide an improved insulator of thiskind.

The invention consists in an insulator so constructed that the surfacein the vicinity of the socket is so shaped that the electric field isdirected almost at right angles to the insulator surface so that lowdischarge alon the surface is preventec l and thus the tension at whichthe spark passes is increased.

In the accompanying diagrammatic drawigure 1 illustrates an insulatoraccording to one form of the present invention;

Fig. 2 shows an explanatory diagram.

In the form of the invention illustrated in Fig. 1 the high tensionconductor d lies centrally within the insulating sleeve a attached to asocket f.

The lines of force due to the electric field between the conductors arerepresented by the lines It and the equi-potential lines by the curves nn.

The insulating sleeve (1 is so shaped that the direction of the fieldespecially at the lower part near the socket f is almost at.

right angles to the surface of the insulator. This results in aninsulator with a comparatively small height for any given diameter and aconcave shape from the exterior aspect.

The explanation of this is as follows In insulating sleeves the glowappearances which start the sparking over extend substantially in thedirection of the lines of force. If then this direction coincides withthe surface of the insulating sleeve as in Specification of LettersPatent.

Patented May 15, 1917.

Application filed November 25, 1913. Serial No. 802,971.

considered to be the socket since the drop in potential per unit ofdistance between the socket and the conductor is greater at this pointthan at some point such as p.

In the spreading of the glow discharge over the surface, first thatportion of .the surface on which the glow appears is renderedelectrically conductive by the ionization of the air. The effective partof the insulator is thereby shortened. For this reason the glowdischarge gradually advances until finally sparks are produced andflashing over takes place.

Now in order to raise the discharging tension for a certain length andheight of insulator, so that the height of the insulator sleeve may bemade as small as possible for a given discharging tension, it isnecessary to avoid entirely if possible, the glow discharge.

This can be effected as described above by making the insulatin sleeveof such a shape as will cause the e ectrical field to be directed almostat right angles to the surface of the insulator especially in thevicinity of the socket, so that the glow discharge and the sparking overwill -"take place through the air and not along the surface of theinsulator.

InFig. 2 if the di-electric constant of the insulator were equal to thatof air, then the lines of force which are produced, will haveapproximately the direction of the curves k, k, whereas theequipotential lines will have the path of the curves n, 11, etc.

Now for the purpose of causing the direction of the field at the socketplace to be at right angles to the surface of the insulator the contourof the surface would tends to keep away from the insulator surface andtherefore does not encourage sparking-over along the insulator surface.

Only in the mid le part of the insulator sleeve near the point marked P,thesurface conforms for ashort distance to the direction of the lines offorce, but it is much less important there because the drop in otentialis not so eat there as at the soc et. Further by suitably shaping, it ispossible to limit this zone and to locate it at a place where the fieldstrength is relativel small.

With this form of insulator there is a considerably smaller ratio, for agiven sparking tension, between height and diameter in the vicinity ofthe socket, than in the usual cylindrical type. This gives also the veryimportant advantage that the place which is the most decisive factor forthe production of glow discharges at the socket and which is marked Q inFig. 1, is surrounded by the insulator surface in such a manner that thefield extending out from this point will enter almost at right anglesinto the insulator wall.

By this means, as has been shown by experiment, the formation of glowdischarges along the surface is entirely obviated, and if the tension issufficiently high,

revolution with a concave outer surface for the maximum part of itslength, the maxi mum diameter being at a position slightly displacedfrom the socket.

In testimony whereof, I aflix my signature in presence of two witnesses.

ALBERT AICHELE. -Witnesses:

CARL GUBLER, AUGUST Riircc.

Copies of this patent may be obtained for five cents each, by addressingthe "Commissioner of Patents, Washington, D. O.

